In a number of industrial processes a relatively cool feed liquid is fed into a vessel and mixed with relatively hot liquid therein. Examples include heat exchangers and steam generators. For example, in a steam generator such as a boiling water nuclear reactor, the heat source is a nuclear fuel core contained in a pressure vessel. Arrangements for effecting the feeding and mixing are well known in the art.
One type of such arrangement includes an inlet conduit connected to the vessel by an inlet nozzle. A sparger disposed within the vessel has at least one outlet port adapted to introduce the feed liquid as a high-velocity jet into the body of liquid in the vessel. A sparger supply line is disposed within the nozzle and places the inlet conduit in flow communication with the sparger so that feed liquid is conducted from the inlet conduit to and through the outlet port. The outer surface of at least a portion of the supply line is spaced from the inner surface of the nozzle to define therebetween an annular cavity opening into the vessel. (Such sparger supply lines are sometimes referred to in the art as "thermal sleeves".) In the prior art arrangements various seals have been employed between an upstream portion of the supply line and the nozzle in attempting to provide arrangements wherein the relatively cool feed liquid is confined within the sparger supply line. Typically, however, such seals have been imperfect, whereby an amount of the feed liquid leaks past the seal. This leakage flow, which as indicated above is relatively cool, flows through the annular cavity adjacently along the inner surface of the nozzle and enters the vessel-contained liquid body adjacent the downstream end of the nozzle, e.g. at the nozzle blend radius. In such arrangements after varying periods of use, cracks have been discovered along the inner surface and blend radius of the inlet nozzle. These cracks are believed to result from thermal cycling of the inner portion of the nozzle by alternate exposure to the hot water or other liquid in the vessel and to the relatively cooler feed water or water cooled by the feed water.
This problem is discussed in greater detail in copending application of Jacobson et al., U.S. Ser. No. 887,471, filed Mar. 17, 1978 now U.S. Pat. No. 4,168,071, assigned to the assignee hereof and incorporated herein by reference. That application describes a thermal isolator arrangement which offers one approach to substantially eliminating thermal cycling of the inner portion of the inlet nozzle and resulting thermal cracking thereof. The present invention is neither disclosed nor suggested by the referenced application.
It has now been found, by practice of the present invention, that the foregoing problem can be substantially overcome by an improvement of the above-described arrangement whereby there is provided an ejector thermal sleeve (ETS) in combination therewith. In a downstream end of the ETS the leakage flow passing the imperfect seal is subjected to the ejective action of the main flow of the feed liquid exiting through the outlet port.